Interventional Pulmonology

Interventional Pulmonology David Hsia,

MD

a,

*, Ali I. Musani,

MD, FCCP

b

KEYWORDS  Interventional pulmonology  Bronchoscopy  Airway  Pleural disease  Procedure

Interventional pulmonology is a rapidly growing procedural-based field that bridges the gap between pulmonary medicine and thoracic surgery. Focusing on minimally invasive methods of diagnosis and treatment, interventional pulmonology spans a wide range of areas within pulmonary medicine, including both malignant and benign diseases. The expansion of this field in recent years has largely been driven by advances in technology and development of novel devices. As a result, in the last several years, interventional pulmonology has extended beyond prior boundaries of therapeutic interventions for central airway and pleural disease to include new diagnostic tools for diagnosing lung lesions and novel therapeutic interventions such as bronchial thermoplasty (BT) for asthma and bronchoscopic lung volume reduction for chronic obstructive pulmonary disease (COPD). Box 1 summarizes the wide range of diagnostic and therapeutic modalities at the disposal of the trained interventional pulmonologist and the variety of diseases that can be treated. Although not all these interventional pulmonary techniques are discussed, the authors aim to introduce prominent interventions within the context of the diseases encountered by the interventionalist. DIAGNOSIS OF PULMONARY LESIONS Peripheral Lung Lesions

Diagnosis of pulmonary lesions has always been a primary concern of the pulmonologist. Lung cancer remains the most common cause of malignancy-related death, with more than 150,000 deaths annually in the United States.1 One in 500 chest radiographs demonstrates a pulmonary nodule,2 with a higher incidence reported on David Hsia has nothing to disclose. Ali I. Musani is a Consultant for Olympus USA, Spiration, Super Dimension, and Cardinal health; he has received honorarium as speaker from Olympus USA, Super Dimension, Bronchus, Asthmatics, and Cardinal health. Received unrestricted educational grants from Olympus USA. Received industry support for a industry sponsored clinical trials from Cardinal Health, Spiration, Asthmatics and Bronchus Inc. a Division of Respiratory and Critical Care Physiology and Medicine, Harbor–University of California, Los Angeles Medical Center, 1000 West Carson Street, Box #405, Torrance, CA 90509, USA b Interventional Pulmonology Program, National Jewish Health, University of Colorado, J 225, Molly Blank, 1400 Jackson Street, Denver, CO 80206, USA * Corresponding author. E-mail address: [email protected] Med Clin N Am 95 (2011) 1095–1114 doi:10.1016/j.mcna.2011.08.002 medical.theclinics.com 0025-7125/11/$ – see front matter Ó 2011 Elsevier Inc. All rights reserved.

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Box 1 Disease states and related interventional pulmonary procedures Diagnosis of pulmonary lesions Peripheral lung lesion Electromagnetic navigation Radial endobronchial ultrasonography Mediastinal adenopathy Linear endobronchial ultrasonography Early detection of lung cancer Autofluorescence bronchoscopy Narrow band imaging Confocal bronchoscopy Central airway obstruction Mechanical debulking and dilation Rigid bronchoscopy Balloon bronchoplasty Microdebridement Stent placement Ablation therapies Endobronchial laser Argon plasma coagulation Electrocautery Cryotherapy Brachytherapy Photodynamic therapy Artificial airway Percutaneous tracheostomy Minitracheostomy Transtracheal oxygen catheter Pleural disease Medical pleuroscopy and pleurodesis Indwelling pleural catheter Thoracic ultrasonography Other diseases Asthma Bronchial thermoplasty Emphysema Endobronchial valve

Interventional Pulmonology

computerized tomographic (CT) imaging.3 In the United States alone, more than 150,000 patients with lung nodules are assessed annually, and this number will likely increase, given results from the National Lung Cancer Screening Trial demonstrating a 20% reduction in mortality with CT scan screening in a high-risk population.4 Nevertheless, routine bronchoscopy has a sensitivity of only 34% for lesions smaller than 20 mm and 63% for lesions larger than 20 mm.5 Diagnostic yield with only fluoroscopic guidance is also notably poor for peripheral lesions, with yields of only 14% for lesions smaller than 20 mm in the outer third compared with 31% for lesions within the proximal two-thirds of the lung parenchyma.6 New technologies have been shown to dramatically increase bronchoscopic diagnostic yield for small peripheral lung lesions. Electromagnetic navigation bronchoscopy

Electromagnetic navigation (EMN) bronchoscopy is a relatively new technology that allows real-time procedural guidance for sampling of peripheral pulmonary lesions. The system uses a high-resolution CT scan of the chest to create a virtual bronchoscopic image of the patient’s tracheobronchial tree. The patient is placed within an electromagnetic field, and the virtual airway map is aligned with the patient’s anatomic airway. The steerable sensor probe is then navigated to the target lesion under virtual real-time guidance. Fig. 1 demonstrates the virtual images created for navigational guidance and the computerized tracking of the distance, direction, and orientation between the steerable sensor probe and the lesion. On reaching the lesion, a guide sheath catheter is left in place, which is used as an extended working channel for obtaining biopsy samples.

Fig. 1. EMN bronchoscopy. A steerable sensor probe is navigated to the target lesion using a virtual map of the tracheobronchial tree generated from the patient’s high-resolution CT scan. Different image displays assist in the navigation process (coronal, axial, and sagittal CT images shown). The system indicates direction, distance, and orientation of the steerable probe to the lesion (bottom right). In this case, the steerable probe (represented by a solid bar on CT images) has been navigated within 0.5 cm of the lesion.

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EMN bronchoscopy can be performed under moderate or deep procedural sedation in the bronchoscopy suite. An early study demonstrated EMN to only add an additional 15 minutes to a conventional bronchoscopic procedure.7 EMN bronchoscopy increases diagnostic yield of peripheral lung nodules to a range of 59% to 77%.7–12 EMN bronchoscopy has also been used for navigational guidance for transbronchial needle aspiration (TBNA) of mediastinal lymph nodes, but its role in lymph node biopsy and mediastinal staging of cancer has largely been overshadowed by linear endobronchial ultrasonography (EBUS)-guided TBNA, which is less expensive and more readily available. EMN has also been used to guide placement of fiducial markers for localized radiation therapy for malignancies and surgical resection. Future uses of navigation techniques such as EMN may merge diagnostic bronchoscopy with therapeutic modalities, such as brachytherapy, to allow minimally invasive diagnosis and therapy for malignant lesions in patients for whom surgical options are limited. Radial EBUS

Radial EBUS produces a 360 image of airways and surrounding structures such as lung parenchyma, blood vessels, lymph nodes, or abnormal lesions (Fig. 2). Radial EBUS images are processed using a processor different from that of the bronchoscopic video image. A 20-MHz mechanical EBUS probe is inserted into a guide sheath catheter and advanced through the flexible bronchoscope working channel. Once the lesion has been located, the guide sheath is left in place and the radial EBUS probe is removed, allowing the guide sheath to be used as an extended working channel for biopsy instruments to obtain tissue samples.13 As with EMN, fluoroscopy can also be used to help visually confirm stability of the guide sheath placement during the biopsy process. Diagnostic bronchoscopic yields of peripheral lung nodules with radial EBUS navigation range from 46% to 88%,13–17 with a recent meta-analysis reporting a pooled sensitivity of 73%.17 Although radial EBUS does not have the benefit of a steerable catheter such as EMN, it has the advantage of real-time radiographic confirmation of localization of the target lesion, whereas EMN is dependent on a virtual target location. Errors in EMN registration between the virtual image and the patient’s anatomy may result in erroneous guide sheath catheter placement and thus biopsy sampling errors. In addition, EMN requires a significant amount of time in the preprocedural planning phase and has the additional cost of the disposable steerable probe. Radial EBUS, on the other hand, uses a reusable probe. Despite their differences, these 2 navigation technologies can be used together as complimentary systems with a higher combined diagnostic yield of 88%.9 On-site analysis of radiographic EBUS images has also been used to predict benign from malignant lesions with an accuracy of nearly 90%.13 However, few bronchoscopists have this level of expertise with image interpretation.

Mediastinal Adenopathy

TBNA is an effective technique for diagnosing mediastinal adenopathy or extraluminal lung masses as well as staging lung cancer. This technique was first described for use with rigid bronchoscopy and adapted for flexible bronchoscopy by Wang and colleagues18 in 1978. There is a wide range of diagnostic yield reported in the literature ranging from 15% to 85%,19,20 and, despite the demonstrated safety and efficacy, this technique has largely been underutilized.21,22 Several modifiable factors have been shown to improve diagnostic yield, including operator experience,23,24 number of aspirates obtained,25 use of rapid on-site cytology,25,26 and larger needle gauge.27–29

Interventional Pulmonology

Fig. 2. Radial EBUS. (A) Therapeutic bronchoscope with a 2.8-mm diameter working channel. The radial EBUS probe and guide sheath (2.6-mm outer diameter) are shown extending beyond the distal tip of the flexible bronchoscope. (B) Example of a different model radial EBUS probe within a guide sheath. (C) Typical snowstorm pattern seen in normal lung. (D) Radial EBUS image of adenocarcinoma.

However, one of the most significant recent advances affecting diagnostic yield is the incorporation of linear EBUS into the procedure. Linear EBUS

Endoscopic ultrasonography (EUS) has been used in gastroenterology, but the miniaturization of ultrasound transducers permit the technique’s use in interventional pulmonology as a radial EBUS probe or by integrating the transducer into a bronchoscope for radiographic evaluation and biopsy of mediastinal lesions. Current EBUS bronchoscopes use a linear (convex) transducer placed in contact with the airway wall. A saline-filled balloon is used to improve contact between the bronchoscope and airway wall, thereby improving image acquisition. These bronchoscopes allow real-time ultrasonography of the mediastinum along with real-time needle aspiration and tissue sampling (Fig. 3). Given the unique characteristics of the EBUS

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Fig. 3. Linear EBUS. (A) EBUS bronchoscope. The linear ultrasound transducer is located in the distal portion of the bronchoscope. Visual optics are oriented at 35 (not shown). (B) EBUS bronchoscope with balloon inserted and catheter deployed. (C) EBUS bronchoscope with saline-filled balloon and needle deployed. (D) Ultrasonographic image of needle aspiration of a lymph node.

bronchoscope, specific training and practice are required to maximize diagnostic yield with this technique. Diagnostic yield of EBUS-guided TBNA has a sensitivity of more than 95%, specificity of 100%, and accuracy of 90%.30 One study reported a sensitivity of 95.3% for non–small cell lung cancer and a negative predictive value of 97.6% after 3 successful aspirations of a lymph node.31 When prospectively compared with conventional TBNA, EBUS-guided TBNA yields were similar for the subcarinal region and higher for all other nodal stations.32 Transesophageal EUS using a specialized endoscope with radial ultrasound transducer has been used by gastroenterologists for biopsy and staging of subcarinal and paraesophageal lesions. A meta-analysis of 18 studies using EUS-guided fine-needle aspiration (FNA) for non–small cell lung cancer staging demonstrated a pooled sensitivity of 83% and specificity of 97%.33 EUS-guided FNA, however, is unable to access the hilar, infrahilar, and intralobar nodes, and, therefore, EBUS and EUS-guided sampling should be considered as complimentary modalities. Studies have now shown that both transbronchial and transesophageal lymph node biopsy can be performed using the same EBUS bronchoscope; this allows an operator to evaluate most mediastinal lymph node stations using the same endoscope in one procedure.34,35 Early Detection of Lung Cancer

Early airway cancers and precancerous lesions may not appear obvious under standard white light imaging but can be accentuated by specialized imaging modalities. Although these conditions primarily involve squamous cell carcinomas and carcinoma in situ, other abnormal epithelial findings such as squamous dysplasia may eventually develop into cancers. The rate of transformation of premalignant lesions into cancer is not well defined but has been observed to occur only in 6.1% of cases.36 The bronchoscopy imaging modalities discussed in this article are approved by the US Food and Drug Administration (FDA) to help identify abnormal lesions for the early detection of cancer.

Interventional Pulmonology

Autofluorescence imaging

Light fluorescence characteristics of abnormal bronchial epithelium have been shown to differ from those of normal tissue, with slightly weaker fluorescence for red wavelengths of light and much weaker fluorescence for green and blue wavelengths. This difference is thought to be related to an increase in epithelial thickness associated with increased blood flow and/or reduced concentration of fluorophores in abnormal tissue.37 Autofluorescence bronchoscopy (AFB) uses a blue light filter to remove other wavelengths of light returning to the bronchoscope. Additional differences in fluorescence characteristics between normal and abnormal tissue can be highlighted using exogenous fluorescent compounds, such as hematoporphyrin derivatives such as 5-aminolevulinic acid. Although AFB has been shown to be superior to white light bronchoscopy alone in detecting early epithelial cancers,37–40 these comparisons were primarily performed with fiberoptic imaging technology, and it is unclear if the benefit is still as notable when compared with higher-resolution video bronchoscopy systems. AFB also requires a separate bronchoscopy system, increasing procedure time and expense; this makes AFB more suitable for a dedicated interventional pulmonology suite. Narrow band imaging

Narrow band imaging (NBI) capitalizes on the increased absorption of blue (415 nm) and green (540 nm) wavelengths of light by hemoglobin. As demonstrated in Fig. 4, atypical mucosal epithelium is associated with increased angiogenesis. These areas are differentially highlighted when white light bronchoscopy is viewed with specific filters.41 Small studies using NBI have demonstrated increased detection rates of dysplasia or malignancy in up to 23% of cases not found using white light bronchoscopy.42 Unlike AFB, NBI is integrated into newer bronchoscope processors, and the transition between white light bronchoscopy and NBI is nominal. NBI technology, however, is proprietary and only available through one manufacturer. Confocal bronchoscopy

Fibered confocal fluorescence microscopy uses a blue laser (440–500 nm) to induce fluorescence. This technology is able to produce dynamic high-resolution microimaging of the respiratory epithelial cells, goblet cells, cilia, smooth muscle, subepithelial

Fig. 4. NBI. (A) White light image of atypical squamous mucosa. (B) NBI of the same atypical mucosa demonstrating the ability of NBI to highlight angiogenesis associated with mucosal malignancies and premalignancies.

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microvasculature, and alveolar ducts and sacs (termed alveoscopy) up to depths of 200 mm.43 This high degree of resolution provides a real-time view of living tissue at almost histologic resolution through a 1-mm fiberoptic miniprobe. The miniprobe incorporates the light source and detector and is introduced through the working channel of the bronchoscope; in the future, the confocal endomicroscope may be incorporated directly into a flexible bronchoscope. Future uses of confocal bronchoscopy may include characterization of airway remodeling in patients with asthma and COPD and detection of dysplastic and malignant changes in airway epithelium.44 In the meantime, confocal bronchoscopy is tempered by the limited areas that can be explored at any given time given the high resolution. Future investigations using advanced imaging modalities may involve use of AFB or NBI to scan large sections of mucosa for areas of abnormality before more detailed investigation by confocal bronchoscopy. Additional imaging technologies, such as optical coherence tomography for use with clinical bronchoscopy, are also being explored.45 At present, most detected lesions represent squamous metaplasia or dysplasia and the significance of intervention for these lesions has not been clearly demonstrated, although patients may be subjected to a greater number of unnecessary biopsies. The role of these adjunct imaging modalities is still being defined, and evidence demonstrating the clinical impact of these advanced imaging technologies is clearly needed.

CENTRAL AIRWAY OBSTRUCTION

Central airway obstructions of the trachea, mainstem bronchi, or other large airways can result from several different diseases, although bronchogenic carcinoma is the most common cause. The incidence of central airway obstruction is not known, but lung cancer trends suggest that the incidence is increasing,46 and approximately 20% to 30% of patients with lung cancer will develop large airway-related complications associated with their disease.47 Aside from malignancy, nonmalignant causes of central airway obstructions include stenosis, strictures, webs, and granulation tissue resulting from endotracheal intubation, tracheostomy, and inflammatory processes such as Wegener granulomatosis, sarcoidosis, relapsing polychondritis, or infections (eg, tuberculosis, histoplasmosis).48 Aside from classifying based on underlying cause, central airway obstructions are also categorized based on the origin of obstruction (ie, endoluminal, extraluminal, mixed) because this affects what therapeutic modalities might be most appropriate for a specific situation. Mechanical Debulking and Dilation Rigid bronchoscopy

Rigid bronchoscopy was initially used by Gustav Killian in 1898 for a foreign body extraction,49 but its popularity as a means to access the airways had waned after the introduction of the flexible bronchoscope in 1967. However, rigid bronchoscopy has several distinct advantages when dealing with central airway obstructions, including the ability to ventilate the patient through the rigid bronchoscope, the ability to use large-caliber suction catheters to aspirate blood and debris, and the ability to use the shaft of the rigid bronchoscope itself to mechanically debulk obstructing tissue and recanulate the airway. The specific safety advantages of rigid bronchoscopy in maintaining the patency of the patient’s airway during a procedure makes it essential in many cases given the potential dire complications associated with therapeutic interventions for central airway obstructions.

Interventional Pulmonology

Aside from mechanical debulking and serial dilation using the rigid bronchoscope to physically remove or compress obstructing tissue, rigid bronchoscopy can also be used in conjunction with other ablative modalities, including ablative therapies controlled via flexible bronchoscopy. Rigid bronchoscopy is also used for placement and removal of airway stents, foreign body extraction, and therapeutic interventions for massive hemoptysis. Rigid bronchoscopy is performed in an operating room setting with general anesthesia. Given the complexity, interventional pulmonologists require specific training on the proper use of rigid bronchoscope. Balloon bronchoplasty

Mechanical debridement and dilation with rigid bronchoscopy can be complicated by the development of mucosal injury and granulation tissue formation.50 Saline-filled balloons are used with either rigid or flexible bronchoscopy to dilate and restore airway patency with lower risk of mucosal trauma and have been effectively used to treat benign stenosis51–53 and malignant obstructions.54 Complications, although rare, include tracheobronchial laceration,55 pneumothorax, pneumomediastinum, and mediastinitis.56 Although balloon bronchoplasty is effective at increasing airway diameter, recurrent stenosis and or granulation tissue often requires the use of other airway interventions, such as stent placement, to maintain long-term lumen patency.57 Microdebridement

Microdebriders have been used previously in otolaryngological procedures and recently in conjunction with rigid bronchoscopy for mechanical debulking. These debriders are composed of a serrated blade rotating at 1000 to 3000 rpm attached to a hollow suction tube and have been used in both malignant and nonmalignant disease.58 Procedures had been limited to the trachea and proximal mainstem bronchi because of the length of the microdebrider (37 cm), but a longer 45-cm device has recently been used to resect a distal left mainstem malignancy.59 One of the benefits of microdebriders is that they are not associated with potential airway fires that can be triggered by thermal ablation modalities used in conjunction with supplemental oxygen.58 However, microdebriders have been associated with inadvertent resection of normal tissue60 and development of pneumomediastinum when used with jet ventilation.61 Stent placement

There are several indications for therapeutic placement of airway stents, including extrinsic compression or mixed extrinsic/intrinsic airway lesions, recurrent endoluminal airway obstructions, inoperable nonmalignant disease, and tracheoesophageal fistulas.62,63 Stents are frequently used in conjunction with other therapies, such as mechanical debulking and/or ablative therapies, to help maintain airway patency.64 Stents are made of silicone, expandable metal mesh (steel or nitinol), or a hybrid combination of covered metal mesh. Self-expanding metal stents and covered metal stents can be placed by either rigid or flexible bronchoscope.65 Silicone stents, however, require rigid bronchoscopy for placement. Like all airway therapeutics, stents have potentially serious associated risks. Epithelialization or tumor growth through the mesh wall of an uncovered stent can result in reobstruction and makes stent removal difficult (Fig. 5). This risk is alleviated by use of a covered metal stent, although granulation tissue can still form at the proximal and distal ends.66 Metal stents are also difficult to remove, with one series of 25 patients (30 stents) requiring piecemeal extraction in 73% of cases. Complications of removal included retained stent pieces, mucosal tearing and bleeding, reobstruction requiring temporary silicone stent placement, need for postoperative mechanical

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Fig. 5. Airway stent complications. (A) Uncovered metal stent in a patient with tracheal obstruction from adenocarcinoma. Stent patency has been compromised by growth of tumor through the stent wall, mucous occlusion, and stent fracture with exposed metal wires. (B) After rigid bronchoscopy with removal of uncovered metal stent, laser ablation, and replacement with a covered metal stent.

ventilation, and tension pneumothorax.67 In 2005, the FDA issued a black box warning against the use of metal stents in patients with nonmalignant disease unless alternative therapies were unavailable.68 Silicone stents, on the other hand, are easier to remove but more likely to migrate, with a migration rate of 9.5% in the largest described series of 677 patients (926 stents).69 Other complications include mucous plugging and development of granulation tissue.70 However, despite these potential complications, airway stents remain an important therapeutic tool for the trained interventional pulmonologist in the management of central airway obstructions. Ablation Therapies

Laser, electrocautery, and argon plasma coagulation (APC) rely on thermal energy for tissue destruction. These modalities can be used with rigid or flexible bronchoscopy to debulk malignant and nonmalignant central airway masses, remove stenotic lesions, and coagulate areas of bleeding. Nonthermal ablative therapies are also available, although many have delayed effects, which limit their utility in the management of acute airway compromise. Each therapy has unique advantages, however, such as the ability of cryotherapy probes to freeze and attach to foreign bodies, assisting in removal. A comparison of ablative therapies is outlined in Table 1. Endobronchial laser

Endobronchial lasers generate a monochromatic beam of light to produce thermal energy resulting in tissue vaporization, necrosis, and coagulation. There are several types of lasers available, and the Nd:YAG laser is the most commonly used by interventional pulmonologists. This laser is ideal because it provides deep tissue penetration (3– 5 mm) as well as good coagulation and hemostasis. The Nd:YAG laser has been shown to successfully recanalize large airway obstructions more than 90% of the time, although success was lower for peripheral lesions (50%–70%) and for lesions with a component of extrinsic airway compression.71 The neodymium:yttrium-aluminum-perovskite laser

Table 1 Comparison of ablation therapies Mechanism of Action

Advantages

Disadvantages

Nd:YAG laser

Noncontact, thermal energy from laser light

Deep tissue penetration and hemostasis, good for major tissue debulking

Potential damage to adjacent tissue

Nd:YAP laser

Noncontact, thermal energy from laser light

Better hemostasis than that of Nd:YAG laser

Less tissue penetration than that of Nd:YAG laser

Carbon dioxide laser

Noncontact, thermal energy from laser light

More precise ablation than that of other lasers, shallow penetration

Minimal hemostasis, bulky equipment limits use in airways

Argon plasma coagulation

Noncontact, thermal energy from ionized argon gas

Good hemostasis, preferential flow to uncoagulated tissue, bends around corners

Shallow penetration, not ideal for major tissue debulking

Electrocautery

Contact, thermal electrical energy

Inexpensive, multiple accessory types for different situations, good hemostasis

Requires frequent cleaning of contact device, less precision than laser

Cryotherapy

Repeated cycles of freezing and thawing

Good for foreign body removal, no risk of airway fire

Not for acute airway use because of delayed tissue destruction, requires follow-up bronchoscopic tissue removal

Brachytherapy

Direct implantation of radiation source into target lesion

Concentrated, long-lasting, localized tissue effect

Higher risk of hemorrhage and other complications

Photodynamic therapy

Preferential uptake of photosensitizer by malignant cells with nonthermal laser–activated phototoxic reaction

Potentially curative for early mucosal squamous cell cancers

Requires follow-up bronchoscopic tissue removal, 4–6 wk of skin photosensitivity

Microdebrider

Mechanical removal of tissue by rotating blade and suction

No risk of airway fire

Device length limits to proximal airway use

Abbreviation: Nd:YAP, neodymium:yttrium-aluminum-perovskite.

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Therapy

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has decreased cutting but improved coagulation. The carbon dioxide (CO2) laser is primarily used by otolaryngologists and has a shallow tissue penetration (0.1–0.5 mm) with very precise cutting but minimal hemostasis; the poor hemostasis qualities and size of the equipment limit CO2 laser use in interventional pulmonology.72,73 Argon Plasma Coagulation

APC uses an argon gas source and electrical generator to create a stream of ionized gas that generates shallow tissue effects (<5 mm) but good hemostasis. Coagulated tissue has higher resistance to current flow compared with uncoagulated tissue, so APC has additional advantages in generating hemostasis. APC preferentially flows toward uncoagulated tissue, including around corners, making it helpful in airways that are anatomically difficult to reach. The relatively decreased ablative qualities, however, make it less ideal for debulking large amounts of tissue.74 Electrocautery

Although laser and APC are noncontact therapeutic modalities, electrocautery is a contact modality that generates thermal energy by the flow of electrons from an electrical generator. In addition to tissue ablation from contact with the electrocautery probe, specialized accessories permit a range of interventions, including cutting of strictures with a cautery knife, biopsy combined with hemostasis with cautery forceps, and resection of polypoid lesions with a cautery snare. Although not as precise as a laser, electrocautery has been shown to be effective in palliation of symptoms related to central airway obstruction with a significantly decreased cost.75 Electrocautery generators often serve a dual use as an APC generator and are commonly found in endoscopy suites for use in both pulmonary and gastroenterology procedures. Caution must be used with all thermal ablation therapies to avoid damage of normal adjacent tissue, perforation of the airways, or hemorrhage.76 In addition, thermal ablation therapies can also damage metal or silicone stents, and extreme caution should be used when these devices are present. Thermal ablation modalities are also contraindicated in patients requiring large amounts of supplemental oxygen given the risk of airway fires, although the risk is low.77,78 Cases of air emboli have been described with APC and Nd:YAG laser.79 PLEURAL DISEASE

Interventional pulmonologists have a wide range of diagnostic and therapeutic pleural procedures at their disposal. Some procedures, such as medical thoracoscopy, have been available for many years and have recently regained interest because of the emphasis on minimally invasive interventions. Other procedures involve adaptations of older devices for novel uses. Medical Thoracoscopy

Medical thoracoscopy, also referred to as pleuroscopy, was initially described by Jacobeus80 in 1910. Medical thoracoscopy can be performed by the interventional pulmonologist under local anesthesia and moderate procedural sedation in an ambulatory procedure suite, unlike video-assisted thoracic surgery (VATS), which requires general anesthesia with double-lumen intubation in an operating room.81,82 Only a single site is required to enter the thoracic cavity rather than multiple incisions required by VATS. Both rigid and semirigid thoracoscopes are available and allow the operator to evaluate the pleural space, obtain targeted pleural biopsies under direct visualization, remove pleural fluid, lyse adhesions, and perform chemical pleurodesis. Diagnostic accuracy of medical thoracoscopy is higher than closed-needle

Interventional Pulmonology

biopsy and has been reported to be as high as 97% for malignant effusions, mesothelioma, and tuberculous-related pleural disease.83 Successful pleurodesis with talc poudrage is achieved in more than 95% of cases at 90 days.84 Lung biopsy85 and management of spontaneous pneumothorax86 have also been described. Potential complications include bleeding, persistent pneumothorax, or damage to intercostals nerves or blood vessels.81 Indwelling Pleural Catheter

Indwelling pleural catheters allow for outpatient management and periodic drainage of malignant and other recurrent pleural effusions. Catheters can be placed in an outpatient setting using local anesthesia and minimal procedural sedation. Up to 100% of patients have control of their effusion-related symptoms, and pleurodesis occurs in approximately 60% of patients over a 4- to 6-week period without additional chemical pleurodesis.87–89 Complication rates are low (<1%) and include pain, cellulitis, and empyema.87,89 OTHER DISEASES Bronchial Thermoplasty

In 2010, BT was approved by the FDA as the first nonpharmacologic treatment of patients with moderate and severe asthma. As shown in Fig. 6, a flexible bronchoscope is used to position an expandable basket to make contact with the walls of the bronchial tree and perform radiofrequency ablation (RFA). Prior animal studies demonstrated that RFA delivered in this manner resulted in a decrease in smooth muscle mass of the airway wall and decreased airway responsiveness to methacholine.90 A total of 3 bronchoscopy procedures are performed to systematically deliver RFA to the bilateral upper and lower lobe bronchi with more than 3 mm in diameter. Clinical trials have recently demonstrated a 32% decrease in severe exacerbations,

Fig. 6. Bronchial thermoplasty. An expandable basket is introduced into the large airways and used to contact airway walls and perform radiofrequency ablation of smooth muscle in patients with moderate and severe asthma.

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84% decrease in emergency room visits, 66% decrease in days lost from work/ school/activities, and a 36% decrease in patient-reported asthma symptoms with BT compared with sham bronchoscopy.91 Benefit from BT is maintained for at least 2 years postprocedure with additional follow-up evaluation ongoing.92 Endobronchial Valve Placement

In 2003, the National Emphysema Treatment Trial demonstrated that lung volume reduction surgery (LVRS) decreased mortality, improved exercise tolerance, and improved quality of life in certain populations of patients with severe emphysema.93 It was then theorized that endoscopically placed endobronchial valves (EBV) would allow 1-way flow of air and secretions, thereby promoting distal airway atelectasis and emulating the effects of LVRS. Results of a prospective randomized trial of unilateral EBV in patients with severe COPD recently demonstrated a mild improvement in lung function and exercise tolerance; however, there was a significantly greater incidence of COPD exacerbations, pneumonia, and hemoptysis in the treatment group compared with the medically treated control group.94 At present, EBV placement for patients with COPD is not yet available for routine use. There are also ongoing evaluations of different valve designs,95 biologic adhesives,96,97 and airway bypass formation.98,99 Of note, EBV placement has also been used to treat bronchopleural fistulas100,101 and are currently approved for postsurgical cases on a humanitarian use basis. INTERVENTIONAL PULMONOLOGY TRAINING

Appropriate use of these advanced interventions requires additional training above and beyond the typical experience provided by most pulmonary and critical care fellowship training programs. At present, there is no structured method of demonstrating competency in these advanced procedures, although the American College of Chest Physicians, the American Thoracic Society, and the European Respiratory Society have published suggested guidelines on advanced procedural competency.76,102 Although formal training in interventional pulmonology is not a requirement to learn specific procedures within the field, additional structured training in advanced interventional pulmonology procedures is becoming recognized as an important, and almost necessary, requirement to ensure competency of the interventional pulmonologist.103 Operator competency, in turn, is essential to ensure optimized procedural efficacy, efficiency, and safety. SUMMARY

In the last decade, interventional pulmonology has grown rapidly fueled by technologic advancements and emphasis on noninvasive procedural interventions. Novel modalities are now being developed for diseases not previously treated by procedural intervention, such as asthma and COPD. In the future, new modalities will undoubtedly become available to the interventional pulmonologist, with current exploratory studies investigating areas such as bronchoscopic use of optical coherence tomography, vibration resonance imaging, and RFA of tumors. In addition, established technologies are being adapted for new indications, such as ablative therapies for pleural diseases. Interventional pulmonology provides a growing spectrum of procedural interventions that supplement standard pulmonologists, radiologists, thoracic surgeons, and otolaryngologists.

Interventional Pulmonology

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